The frequency band of Bluetooth is 2400-2483.5MHz (including the protection frequency band). This is a 2.4 GHz short-range radio band, and it is an industrial, scientific and medical (ISM) band that does not need permission (but is not unregulated) on a global scale.
Bluetooth uses frequency hopping technology to divide the transmitted data into data packets, and transmits the data packets through 79 designated Bluetooth channels. The bandwidth of each channel is 1 MHz. Bluetooth 4.0 uses a spacing of 2 MHz and can accommodate 40 channels. The first channel starts at 2402 MHz and reaches 2480 MHz every 1 MHz. Using the adaptive frequency hopping (AFH) function, it usually hops 1600 times per second.
At first, Gaussian frequency shift keying (GFSK) modulation was the only available modulation scheme. However, Bluetooth 2.0+EDR makes it possible to use π/4 DQPSK and 8DPSK modulation in compatible devices. It is said that the devices running GFSK can run at the basic rate (BR), and the instantaneous rate can reach1mbit/s. The term enhanced data rate (EDR) is used to describe π/4-DPSK and 8DPSK schemes, which can reach 2 and 3Mbit/s respectively. In Bluetooth radio technology, the combination of two modes (BR and EDR) is collectively called "BR/EDR RF".